Use the Google Cloud API to upload and download files to/from a bucket using explicit authentication in a C# app.

GoogleCloudStorageFileExhange.cs

using Google.Apis.Auth.OAuth2; // Google.Apis.Auth --version 1.30.0
using Google.Cloud.Storage.V1; // Google.Cloud.Storage.V1
using System;
using System.IO;
using System.Runtime.InteropServices;
using static System.Console;

public static class Program
{
  public static void Main(string[] args)
  {
    string message = "Dot Net example: Upload file to Google Cloud Bucket. And also download";

    string bucketName = "my-bucket";

    // Explicitly use service account credentials by specifying the private key file.
    // The service account should have Object Manage permissions for the bucket.
    GoogleCredential credential = null;
    using (var jsonStream = new FileStream("credentials.json", FileMode.Open,
        FileAccess.Read, FileShare.Read))
    {
        credential = GoogleCredential.FromStream(jsonStream);
    }
    var storageClient = StorageClient.Create(credential);

    using (var fileStream = new FileStream("Program.cs", FileMode.Open,
        FileAccess.Read, FileShare.Read))
    {
        storageClient.UploadObject(bucketName, "Program.cs", "text/plain", fileStream);
    }

    // List objects
    foreach (var obj in storageClient.ListObjects(bucketName, ""))
    {
        Console.WriteLine(obj.Name);
    }

    // Download file
    using (var fileStream = File.Create("Program-copy.cs"))
    {
        storageClient.DownloadObject(bucketName, "Program.cs", fileStream);
    }

    foreach (var obj in Directory.GetFiles("."))
    {
        Console.WriteLine(obj);
    }

    WriteLine("**Environment**");
    WriteLine($"Platform: .NET Core 2.0");
    WriteLine($"OS: {RuntimeInformation.OSDescription}");
    WriteLine(message);
    WriteLine();
  }
}

amazing! Thanks :)